Useful technologies

WebSockets: can be used for real-time communication between a player and the game server, to support multi-player games.

Node.js: Node is often used as a multiplayer game server, controlling the logic and handling the WebSockets connections to the players. It can be used for player authentication and the storage of data so game play can persist over multiple game sessions. This is all made relatively easy with great third-party modules, like Socket.IO for WebSockets, and others that handle Redis and MongoDB for storage, for example.

DOM Storage is great for storing data locally on the player's device. This way you can cache game data and allow the game to pick up where the player left off.

The Full Screen API allows you to expand any HTML element to ﬁll the user's screen, even if the browser isn’t running full-screen itself. The Mozilla implementation is not perfect yet because you can’t use the whole key board in full-screen mode, but it’s in the latest Nightly builds and works in all other respects.

Application cache: One of the main differences between Web apps and native apps is that native apps can be run offline. New technologies like the application cache allow for a website or a Web app to cache necessary assets so it can still run while offline. This includes things like JavaScript ﬁles, CSS and images. Combining this technique with intelligent use of things like localStorage will allow your game to continue working even if the Internet connection goes down. You just sync up all the changes when it gets connected again.

Emscripten enables you to port a game written in C or C++ over to JavaScript. The Bananabread demo used Emscripten.

Not every browser supports every part of HTML5. For example, Canvas isn’t supported out of the box by any Internet Explorer below version 9. However, you can use Explorer Canvas to replicate canvas functionality (but that is not ideal and does not perform as well). WebSockets is supported by IE only in IE 10, and it isn’t supported in the stock browser of Android. But again, you can fake this by using Flash for the sockets, such as with Socket.IO. WebGL has patchy support; Safari and Opera have it disabled by default and Internet Explorer requires at least version 11.

Game template

You can use the Mortar Game Stub template to get a quick start on an HTML5 game, or you can use it to get ideas on best practices.

Future APIs

The Gamepad API is one of the major improvements to input that is coming. Both Google and Mozilla are working on implementations of this and, as of Firefox 24, is available but disabled by default (to enable, set dom.gamepad.enabled in about:config to true, see bug 878828). What is most interesting about the Gamepad API is that it might be just what ﬁnally justifies HTML5 gaming on a TV or console. Who wants to use a keyboard and mouse while sitting on the sofa?

The Pointer Lock API is an attempt to improve the mouse as an input device. It would be used in situations like games and 3-D visualizations where the mouse position rotates or moves you around a 3-D space. As it stands, there would still be a cursor moving around the screen causing all sorts of trouble when you want to click on something in your game. With the new API you can lock your mouse position and stop it from getting in the way and being a nuisance.